Orthodontics I Course Review Enoch Ng, DDS 2014 Intro to Ortho - Tooth size and number decreasing, but slower than jaw size o From softer foods, refined sugars, genetics - Population Stats o 45% people have ideal Mx occlusion = 55% people have Mx crowding o 35% people have ideal Mn occlusion = 65% people have Mn crowding o 45-55% people have ideal OJ, 15% have class II, <5% have class III o 50% people have ideal OB, 30% have deep bite, <5% have open bites . Problems happen from deep bites, not open bites - Angle’s Occlusion . US population, classification of anterior teeth only (did not look at molars) o 30% normal o 55% class I malocclusion o 15% class II o <1% class III Bone Biology - Flat bones – intramembranous – direct ossification without cartilage template – cranial vault, Mn body, Mx - Long bones – endochondral – indirect ossification, requires cartilage – femur, cranial base, condyle o Complex multistep, sequential formation/degradation of cartilage, postnatal growth and repair - Ages o 0-20y/o = BF>BR o 20-50y/o = BF=BR o >50y/o = BF<BR - Osteoclasts needed for bone formation – osteoclastic number (not activity) control bone formation - Drugs o Bisphosphonates – osteoporosis . Nitrogen containing = affects ruffled membrane . Non-nitrogen containing = causes cell death o Glucocorticosteroids – arthritis Orthodontics I Course Review Enoch Ng, DDS 2014 Craniofacial Growth/Development 1 - Cephalocaudal gradient (head to tail bone) o 2 months = 50% head o Birth = 30% head . Head bigger than face (small Mn) = easier to get through birth canal o 25y/o = 12.5% head . Cranium closest to adult size at birth, stops growing first . Mn last bone to finish growing - Scammon’s Curve o 7y/o – cranial sutures close, neural development finished, ideal time to screen for ortho o 10y/o – lymphatics done, start to shrink o 10-12y/o – puberty starts, genital and general growth spurts begin - Growth Patterns o Boys start developing 2 years later, develop for longer, and grow larger than girls o Growth spurt starts 2 years before sexual maturation - Apposition – periosteum experiences hyperplasia, hypertrophy, and ECM secretion at surfaces (not internally) Craniofacial Growth/Development 2 - Cranial vault – intramembranous formation/ossification, growth at sutures and apposition along fontanelles, resorption along internal surface - Cranial base – endochondral from spheno-occipital, intersphenoid, and spheno-ethmoidal synchondroses o Growth stops at age 7 - Mx is displaced anterior inferiorly, with resorption along anterior surface and apposition on posterior surfaces o Best age to pull Mx forward is age 7 o Palatal sutures close around 13-15 y/o o Lengthening of Mx arch from apposition along Mx tuberosity - Mn intramembranous formation . Mn ramus = intramembranous ossification, condyle = endochondral ossification o Apposition along posterior surface, resorption along anterior surface of ramus (space for 3rd molars) - For young kids, growth of the alveolar process is most important to accommodate the developing dentition - Soft tissue – loses collagen with age o Sags – decreased exposure of upper incisors and increased exposure of lower ones o Thinner, less vermillion displace, less protruded - Cartilage growth o Nasal bone growth stops at age 10, cartilage finishes after adolescent growth spurt o Females = stops age 17-19/o o Males = stops age 19-21y/o - Mn crowding – late Mn growth = crowding earlier, but may resolve later on o Bones stop growing in width first, then in length. Growth in height is the last to stop - Adolescence - Adults o Treat females around 2y earlier than boys o Facial tissue grows more than hard tissue o Lots of individual variation o Lower incisal crowding o Mid-palatal suture close 13-15y/o o Lip line to upper incisors o Mn last bone to grow o Chin accentuation o Space for 3rd molars Orthodontics I Course Review Enoch Ng, DDS 2014 Development of Dentition 1 - Stages of Development o Primary dentition o Early mixed – presence of permanent incisors and molars o Late mixed – loss of deciduous molars and canines o Permanent dentition - Primary dentition o Centrals, laterals, 1st molars, canines, 2nd molars . 4 month rule . Variations of up to 6m for eruption normal . Dentition is stable from 3-6 y/o – development of permanent dentition o Primate space = M to canine in Mx, D to canine in Mn o Shallow overbite/excess overjet o Increased horizontal overlap of anterior teeth . Mx grows AP faster than vertically - 71% Flush terminal plane – class I or II - 19% Mesial step – class I or III - 10% Distal step – class II - Primary dentition less proclined than permanent dentition o Permanent arches are more tapered, primary arches are more ovoid - Leeway space – space from difference in size between primary and permanent teeth . C (canine) = 0 . D (premolar 1) – Mx = 0.0mm, Mn = 0.5mm . E (premolar 2) – Mx = 1.5mm, Mn = 2.0mm o Mn arch = 5mm leeway space o Mx arch = 3mm leeway space - Mesial shifting o Early mesial shift (63% of population) – mesial migration of Mn 1st molar . Uses up primate space, occurs around age 6 o Late mesial shift (100% of population) – mesial migration of Mn 1st molar AFTER primary 2nd molar loss . Uses up leeway space, occurs around age 11 - Teeth move occusally, mesially, buccally in adulthood Orthodontics I Course Review Enoch Ng, DDS 2014 Development of Dentition 2 - 1st molars, Mn centrals, Mx centrals, Mn laterals, Mx laterals, Mn canines, Mx premolars, Mn premolars, Mx canines, 2nd molars, 3rd molars - 3 principles of treatment planning impacted teeth o Prognosis related to extent of displacement and surgical trauma o Eruption should happen through keratinized mucosa o Adequate space created prior to surgery - Transitional midline diastema – closes with eruption of Mx canines o >2mm = begin pondering treatment - Dental arch length decreases with transition from primary to permanent dentition - Incisor liability – canine eruption, primate spacing, incisor proclination - Potential problems with eruption o Premature loss of deciduous teeth – if primary 2nd molar is lost, ALWAYS maintain the space o Interproximal decay, over-retained primary teeth o Impaction – contralateral teeth should erupt within 6months of each other o Ankylosis – grey in color, dull to percussion o Positional anomalies – ectopic eruption (wrong location) of lower incisors . Transposition – most commonly upper lateral and canine . Palatal eruption – may be genetic . Canines erupted in line, but if crowded likely to erupt labially o Crossbites (posterior and/or anterior) Orthodontics I Course Review Enoch Ng, DDS 2014 Biology of Tooth Movement - PDL required, acts as a shock absorber - Physiologic function – fast (<5s) and heavy loading, intermittent o Fluids and ligaments stabilize against gross displacement, alveolar bone bends, no pain - Undermining resorption o Heavy forces, rapid pain, compressed PDL decreases bloodflow = necrosis hyalinization of tissue o Takes longer to move tooth – must heal first - Frontal resorption o Light forces, relatively painless, reduced blood flow causing signaling, not cell death, remodeling occurs o Tension and compression sides for remodeling . Tension = apposition – osteoblasts and fibroblasts, laying down osteoid . Compression = resorption – osteoclasts o Minimum 4-6h to get orthodontic tooth movement, want around 20-350grams of force - Tissue changes o Enamel = no effect o Cementum = localized perforations, repaired from cellular cementum zone o Dentin = resorption possible in areas of perforated cementum o Pulp = transitory inflammation – loss of tooth vitality in teeth with history of trauma - Types of movement o Tipping o Translation o Rotation o Extrusion o Intrusion - Force types o Continuous force – never declines to zero. Think of a NiTi coil spring o Interrupted force – declines to zero, then replaced. Think of a power chain o Intermittent force – declines to zero, but appliance is removable. Think of headgear or elastics - Drugs . Prostaglandins and IL1β increases quickly in PDL during orthodontic tooth movement . Prefer to use Tylenol instead of NSAIDs, as NSAIDs act centrally and block prostaglandins o Depress OTM . Bisphosphonates, prostaglandin inhibitors (NSAIDs), tricyclic antidepressants, antyarrhythmics, glucocorticosteroids, antimalarials, anticonvulsants, tetracyclines o Increase OTM . Vitamin D, prostaglandins Orthodontics I Course Review Enoch Ng, DDS 2014 Patient Exam and Diagnosis - Psychosocial o Develop rapport with patient o Write down the CC verbatim, ADDRESS THE CC . Why are you here? Why now? What do your parents say? . Why do you think you need braces? o MHx/DHx - 3 major reasons for ortho treatment o Impaired dentofacial esthetics o Impaired function o Enhancement of dentofacial esthetics - Be problem oriented so as not to fixate on only 1 portion – idea is to create a database for planning o Prioritize the problem list – should address primary CC, ensures all issues are addressed, includes pathologic, functional, and developmental problems - Patient interview o Physical growth evaluation – growth charts, sexual maturation, growth prediction o Social/behavior evaluation – internal motivation/expectation, documentation of patient compliance, etc - Clinical Exam o Oral health – perio charting, caries, pulpal disease o Jaw and occlusion – mastication/speech, habits, breathing, TMD/other dysfunctions o Facial/dental appearance . Macroesthetics – frontal exam (symmetry, proportions of width/height), developmental age, facial proportions, profile analysis